Mom’s circadian rhythm could be root cause of premature birth, study shows

Women’s body clocks could hold the key to preventing premature births, according to new research. Maternal circadian rhythms govern the unborn baby’s biological clock before it starts ticking on its own.

The findings suggest that female shift workers, such as nurses and flight attendants who work on long-distance routes, could be most prone to pregnancy complications.

Scientists say the suprachiasmatic nucleus – SCN for short – makes everything in the body run on time. It lies in the hippocampus — the memory center of the brain — and regulates sleep, hunger, hormone levels, body temperature, cell cycles and more. But experiments on rats found while the fetal clock develops, it is mom’s behavior that “tells the time.”

“Our data reveal in development in the fetal SCN, maternal stimuli may substitute for an absent intercellular web of synapses and drive cell-population rhythms before the clock fully mature,” the authors, based at the Czech Academy of Sciences in Prague, write. “Because the rats used in these experiments have a gestational period of about 21 days, and the fetuses were examined at 19 days, these results may have implications for premature human babies.”

The team compared the pattern of gene activity in SCN tissue from fetuses developing within pregnant rats kept in the dark, under two sets of conditions. Some had their SCNs disrupted, but access to food limited to eight hours per day. This imposed a circadian rhythm in their activity that their SCNs could no longer sustain.

A control group had intact SCNs and free access to food.

The study found that within SCNs of both sets, there were a few genes whose timing pattern differed between the groups. Most oscillated in sync with each other. Many of these were involved in neuronal development and function. They likely reflect the ongoing development of the SCN as it wires itself up, and the earliest manifestation of mature function.

“The unexpected broadness and specificity of responsiveness of the SCN cells to maternal signals stresses the importance of a healthy maternal circadian system during pregnancy, and points at the potential impact of the absence of such signals in prematurely delivered children,” the authors write. “Our study reveals that distinct maternal signals rhythmically control a variety of neuronal processes in the fetal rat SCN before they begin to operate as the central circadian clock. The results indicate the importance of a well-functioning maternal biological clock in providing rhythmic environment during the fetal brain development.”

Previous research has shown shiftworkers have fertility and menstrual issues. They are habitually out of sync with the external light cycle. It is only in the last decade that the role that disruption to the circadian rhythm may play in their reproductive problems has been investigated.

A 2013 study by the University of Southampton suggests they find it 80 percent harder to have a baby. A year earlier U.S. scientists found mice subjected to advances of the light-dark cycle had a pregnancy success rate of only 22 percent.

The study is published in the journal in PLoS Biology.

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